Motor vehicles include multiple systems where it is beneficial to sense the position or state of a spinning or rotating components. For example, spinning components are used in locking differentials, axle disconnect systems and power take off units. Sensing the position or state of spinning components can be difficult. In locking differentials specifically, spinning gears can be moved in and out of engagement with other gears. The distance between the gears can be indirectly measured when the gears are engaged by measuring the effects of the engagement. However, in some arrangements, the conditions required to indirectly measure the effects of engagement may not always be met. Thus, the only definitive way to determine if the gears have engaged is to measure the distance traveled by the moving/spinning gear.
A current method for sensing the position of spinning components uses sensors mounted rigidly around the spinning component, and the sensors translate the movement of the spinning component tom-non-spinning component. The translation from spinning to non-spinning introduces significant error and cost. For example, any run-out of the spinning component will appear to be small axial movements and, thus, added noise to the measured signal increasing error. These translating sensing systems also have several additional components, each that can add additional noise and cost to the system. Additionally, there is contact between a spinning component and a non-spinning components creating additional wear that decreases the life of the system and increases the cost of the system.
A potential solution is to embed the sensor with the spinning components, allowing the sensor to spin along with the components; however, difficulties arise in getting power to the sensor and transmitting the signal out of the sensor. Wired sensor systems do not work because the wires will quickly wrap around the spinning components.
Therefore, it would be desirable to have a wireless system that directly senses the displacement of the spinning component.